Rotary hook and bobbin-case device for sewing machines



March 19, 1935. c. A. KESSLER ROTARY HOOK AND BOBBIN CASE DEVICE FORSEWING MACHINES Filed May 12, 1934 2 Sheets-Sheet 1 March 19, 1935.

c. A. KESSLER} ROTARY HOOK AND BOBBIN CASE DEVICE FOR SEWING MACHINESFiled May 12, 1954 2 Sheets-Sheet 2 M, MW m w Patented Mar. 19, 1935UNITED STATES ROTARY HOOK AND BOBBIN-OASE DEVICE FOR SEWING MACHINESCharles A. Kessler, Plainfield, N. J., assignor to The SingerManufacturing Company, Elizabeth, N. J., a corporation of New JerseyApplication May 12, 1934, Serial Nd. 725,282

A 12 Claims. (01.112-228) This invention relates to. rotary hook andbobbin-case devices for sewing machines and more particularly tocup-shaped rotary hooks of the horizontal axis type making a pluralityof rotations to one reciprocation of theusual sewing machine needle andhaving a loop-seizing beak arranged to cast the work-limb of the seizedneedle-loop in front of the rim of the hook-body and the take-up limb ofthe seized needle-loop in rear of the bobbin-case within the hook-body;a hook of this type being disclosed in the patents to Diehl et al., No.1,125,669, dated Jan. 19, 1915, and No. 1,149,504, dated Aug. 10, 1915.

A rotary hook of the type in question is provided with a circularraceway in which is journaled the peripheral bearing rib of asubstantially cylindrical bobbin-case restrained -by suitable meansagainst rotation with the hook proper. The'bobbin-case carries a bobbinof thread and the function of the rotary hook is to seize a loop ofthread from the sewing machine needle, draw out-or expand such loop andcast it about the bobbin-case, after which the usual needlethreadtake-up comes into action to draw the loop up to the work and completethe stitch;

There are certain aims in the construction of a rotary hook andbobbin-case device which are well recognized as being desirable ofaccomplishment. For example, to avoid chafing of the needle-threadcaused by the reeving of ,an excessive length of such thread through theeye of the needle and to keep the stroke of the usual vibratory take-upas small as possible, it is desirable that the size or diameter of therotary book be comparatively small so that it will not draw out a largeneedle-loop. Nevertheless, to avoid the necessity of frequentreplenishment of the bobbin -thread supply, it is desirable that thebobbin-case be as large as possible, both in diameter' and length, andthat waste. space between the bobbin-cavity in the bobbin-case and theinner wall of the rotary hook be reduced as much as possible.

It is'a recognized fact that the larger the bobbin, both in diameter andlength, within a rotary book of .given size, the greater is thedifiiculty of providing for the spreading or expansion of theneedle-loop so that it may be freely cast about the bobbin-case.Excessive impedance by the bobbin-case of the casting of the thread-loopthereabout, necessitates the application of an excessive tension to theneedlethread to prevent excessive wrapping of one or both limbs of thethread-loop circumferentially of the bobbin-case prior to the casting ofthe loop onto the outer and inner faces of the bobbincase, whichcircumferential wrapping of the thread unduly enlarges the needle-loopand steals thread from the supply, causing looping, a faultcharacterized by failure of the needle-loops to be drawn-fully up to thework by the take-up, particularly when the machine is operated at highspeed.

The application of a heavy tension to the needle-thread to avoid loopinggreatly restricts the field of usefulness of the machine and limits itto the use of comparatively costly thread of high quality. A heavytension also tends to untwist a thread drawn through it, and for thisreason it has heretofore been exceedingly difiicult to provide a rotaryhook mechanism which will sew thread of either direction of twist withequal facility at high speed.

The present invention has for an object to provide a rotary hook andbobbin-case device of the type disclosed in said Diehl et a1. patentswhich operates in conjunction with the usual reciprocatory needle,take-up and needle-thread tension-device to sew with needle-thread ofpoor quality and either direction of twist, and without looping, athigher speeds than'have heretofore been attained and without theapplication of a heavy tension to theneedle-thread.

A further object of the invention is to im prove the means for guidingand tensioning the bobbin-thread .to gain uniformity in the setting ofthe stitches regardless of speed or other variations in sewingconditions.

With the above and other objects in view, as will hereinafter appear,the invention comprises the devices, combinations, and arrangements ofparts hereinafter set forth and illustrated in the accompanying drawingsof a. preferred embodiment of the invention from which the severalfeatures of the invention and the advantages attained thereby will bereadily understood by those skilled in the art.

In the accompanying drawings, 1 is an outer or front face elevation of arotary hook and bobbin-case device embodying the invention. Fig. 2 is aninner face view of the bobbin-case, with the rotary hook-body insection, showing a seized and partially expanded needle-loop just priorto the casting of the inner or take-up limb of the needle-loop off ofthe outer peripheral wall of the bobbin-case and over the innerperipheral edge of the bobbin-case onto the inner face of the latter.Fig. 3 is a view similar to Fig. 2 showing the inner or take-up limb ofthe needle-loop sion-carrying element of the bobbin-case.

-18 is a perspective view of the bobbin, and Fig.

after it has been cast off of the peripheral wall of the bobbin-case andonto the inner face of the latter. Fig. 4 is a perspective view of thehook and bobbin-case showing the inner or take-up limb of theneedle-loop at the cast-on position relative to the bobbin-case. sembledperspective view of the two-part bobbin-case. Fig. 6 is an inner faceview of that element of the bobbin-case which has a bearing ribjournaled in the hook raceway. Figs. 7, 8 and 9am, respectively,sections on the lines 77, 8-8 and 99, of Fig. 6.

Fig. 10 is a section on the line 10-10, Fig. 8. Figs. 11 and 12 are sideelevations of the bearingrib carrying element of the bobbin-case. Fig.13 is a top plan view of the rotary hook in loopseizing positionrelative to the sewing machine needle. Fig. 14 is a fragmentary frontface view of the bearing-rib carrying element of the bobbin-case. Fig.15 is a section on the line 15-15, Fig. 14. Fig. 16 is a section on theline 16-16, Fig. 14. Fig. 17 is a perspective view of the ten- 19 is alongitudinal peripheral section through the bobbin-threadtension-device.

1 represents the reciprocatory needle of the conventional rotary hooksewing machine having the throat-plate 2 formed with the usual,

needle-hole 3 and feed-dog clearance slots 4. The machine has the usualhorizontal hook-shaft 5 which makes two rotations to each completereciprocation of the needle 1.

Mounted on the hook-shaft 5 is the cup-shaped hook-body 6 having abobbin-case raceway 7 and cut away at one side to provide a loop-seizingbeak 8 having an inclined loop-spreading inner edge 9 crossing the planeof the raceway 7 and preferably reversely curved at 10, 10 between thepoint of the hook-beak and the point where the inclined edge 9 crossesthe plane of the raceway 7. This reverse curvature of the inclinedloopspreading edge 9' permits the shortening of the point of the hookrelative to the bottom 11 of the loop-casting throat 12, without makingthe point of the hook so blunt that it will not safely enter and seizethe needle-loop, and without increasing the angle of inclination of theloop-spreading edge 9 in thatportion thereof adjacent the bottom 11ofithe throat 12 which determines the width of spread of the seizedneedle-loop and must be suflicient to carry the inner limb e of theneedle-loop onto the chamfer 31 to be described. 'In the presentinstance the angle 9 between the hook point and the bottom 11 of theloop-casting throat 12 is less than 30; affording an exceptionally shorthook. By shortening the hook it is possible to advance the timedposition of the hook on the shaft 5 and thus secure an earlier castingof the needle-loop about the bobbin-case, giving more time for thetake-up to act to draw the thread-loop up to the work.

Journaled in the hook-raceway '7 is the peripheral bearing rib 13 of thecup-shaped bobbincase element 14 which has an outer cylindrical wall 15carrying the bearing rib l3 and bridging the usual .gap formed in therib 13 to provide the well known loop-detaining spur 16. The bobbincaseelement 14 has at the outer edge of its rim a flange 17 having in itsouter or front face a rotation-restraining notch 18 entered by a tongue19, Fig. 1, on the usual rotation-restraining bar 20 of the sewingmachine. The flange 17, Figs. 14; 15 and 16, is formed adjacent thenotch 18 with a bobbin-thread guiding slot 21 which is Fig. 5 is adisas.

separate and distinct from the rotation-restraining notch 18 and has aninclined bottom 22, Fig. 16, leading upwardly and outwardly from a pointwell within the inner cylindrical wall 23 of the bobbin-case element 14.

The bobbin-case element 14 has an open inner face crossed by a diameterbar 24 supporting the usual center stud 25 having at its free end alocking groove 26 for the usual spring-pressed latch-slide 27 of themating bobbin-case element 28 carrying the bobbin 29 and thebobbin-thread tension device 30, to be described.

An important feature of .the present bobbincase resides in the chamfer31 adjacent the inner edge 32 of the bearing-rib-carrying element 14 ofthe bobbin-case, in that region within the first 150 past theloop-seizing position of the hook, which chamfer provides a sharplydefined needle-loop cast-on corner 33 beginning approximately at theangular position a, Fig. 6, which is preferably about 60 past thevertical position v and extending in the direction of rotation of thehook-body; said corner being preferably gradually inclined toward theinner edge 32 of the bobbin-case to a point about 120 past the verticaland then sharply or abruptly inclined at 0, toward said inner edge 32'with which said corner merges in the general direction of rotation ofthe hook-body 6. To provide the abruptly inclined portion 0 of thecast-on corner 33, the chamfer 31 preferably terminates in a concaveportion d, Fig. 10, ground on a radius r, of approximately the radius ofthe bobbin-case and at an angle of approximately 45 to the inner wall 23of the bobbin-case element 14, as shown in Fig. 8. The concave terminalportion d of the chamfer and the abruptly inclined terminal portion c ofthe cast-on corner 33 are preferably disposed in the region ofapproximately 120-l30 past the vertical.

The chamfer 31, at its beginning end, at about the angular position a,Fig. 6, is at an angle of about or somewhat less, to the innercylindrical wall 23 of the bobbin-case element 14. From this point onthe angle of the chamfer is gradually increased until the concaveterminal portion d is reached, where the angle of chamfer is preferablyabout The abruptly inclined terminal portion 0 of the cast-on corner 33,as shown in Figs. 2, 3 and 4, is engaged by the inner or take-up limb eof the needle-loop after such loop has been well drawn out by therotary-hook and suddenly casts such limb over the inner edge of thebobbin-case and onto the inner face of the latter. This caston actionoccurs rather suddenly while the hook is traveling the relatively shortdistance between the positions shown in Figs. 2 and 3 and is helped bythe fact that the take-up limb e, of the needleloop is slidinglongitudinally of itself peripherally of the bobbin-case, Fig. 2, and isthus more easily directed inwardly of the bobbin-case by the inclinedcast-on corner 33, without reeving over the latter. At the time thecast-on action occurs, the needle-loop is well drawn out but not fullyexpanded and the amount of thread additionally required to cast the loopabout the bobbin-caseis about equal to that additionally pulled off bythe initial wrapping of the inner limb e of the needle-loop peripherallyof the bobbin-case, as shown in Fig. 2, before such limb e encountersthe sharply inclined portion d of the cast-on corner 33. e

The inclined loop-spreading edge 9 of the hook-beak is only required tospread the needleloop sufficiently to carry the loop into engagementwith the loop-detaining spur 16 and thereafter lay the innerloop-lirnb eonto the beginning end of the chamfer 31. From this point on, thegradually inclined portion of the loopcaston corner 33 prevents theinner loop-limb e from wrapping around the cylindrical portion of thebobbin-case between the bearing'rib 13 and the chamfer 31. When theloop-limb e encounters the more abruptly inclined portion 0 of thecast-on corner 33 it is suddenly forced off of the chamfered portion 31and is cast onto the inner face of the bobbin-case, as previouslydescribed.

The mating section 28 of the bobbin-case is also cup-shaped, as shown inFig. 1'7, and hasin its rim an inclined thread-slot 34 terminating underthe tension-spring 30 in a short peripherally extending portion 35beyond which is a clearance slot 36 .for the downturned free end 37 ofthe tension-spring 30 which has a threadguiding or delivery slot 38arranged to deliver the bobbin-thread to the bottom of the groove 21 inthe bobbin-case element 14, without exposing the bobbin thread at anypoint below the top of the bobbin-case to the wiping action of the outerlimb 1 of the needle-loop. Such wiping action has heretofore prove-dtroublesome as it tends to displace the bobbin-thread and carry it intothe rotation-restraining notch 18 where it interferes with the freeescape of the needleloop.

The tension-spring 30 has the usual fastening screw 39 andtension-adjusting screw 40 and is formed at its free end within thethread-delivery slot 38 with an inwardly depressed transverse rib 41which presses upon the bobbin-'- thread at a predetermined and fixedpoint for all adjustments of thetension-spring and tensions thebobbin-thread more uniformly for a given adjustment, in accordance withthe principlesv disclosed in the Barron Patent No. 1,879,023, of Sept.27, 1932.

The invention is not to be understood as limited to the details ofconstruction and relative arrangements and proportions of parts of thepreferred embodiment thereof shown and described, asmodificationsthereof may obviously be made by those skilled in the artwithin the spirit and scope of the invention.

Having thus set forth the nature vention, what I claim herein is:

l. A horizontal-axis cup-shaped rotary hook for sewing machines having aloop-seizing beak and a raceway, a substantially cylindrical stationarybobbin-case having a peripheral bearing rib journaled in said raceway,said bearing rib having a gap therein providing a stationary spur at apoint beyond the loop-seizing position of the hook-beak to detain theneedle-loop seized by the hook-beak while the hook in its continuedmovement draws out the needle-loop for passage about the bobbin-case,the substantially cylindrical Wall of said bobbin-case being chamferedadjacent the inner edge of the latter to provide a cast-on cornerinclined toward and meeting the inner edge of said bobbin-case in thegeneral direction of rotation of said hook.

2. A horizontal-axis cup-shaped rotary hook for sewing machines having aloop-seizing beak and a raceway, a substantially cylindrical stationarybobbin-case having a peripheral bearing rib journaled in said raceway,said bearing rib having a gap therein providing a stationary spur at apoint beyond the loop-seizing position of the of the inhook-beak todetain the needle-loop seized by the hook-beak while the hook in itscontinued movement draws out the needle-loop for passage about thebobbin-case, the substantially cylindrical wall of said bobbin-casebeing chamfered adjacent the inner edge of the latter to provide acast-on corner inclined toward and meeting the inner edge of saidbobbin-case in the general direction of rotation of said hook, the angleof the chamfer referred to the inner cylindrical wall of the bobbin-casebeing gradually increased from the beginning end of the chamfer towardthe terminal point thereof.

3. A horizontal axis rotary hook for sewing machines having a cup-shapedbody providedwith a loop-seizing beak arranged to cast the work-limb ofa needle-thread-loop in front of the rim of the hook -body, abobbin-case journaled in said hook and restrained against rotationtherewith, said bobbin-case peripherally having a needle-thread-loopdetaining spur and a cylindrical wall adjacent to said spur andextending inwardly of the hook-body, said cylindrical wall having withinthe width thereof a circumferentially extending cast-on corner spacedfrom said spur axially of the bobbin-case and terminating in the innerrim of the bobbin-case.

4. A horizontal axis rotary hook'for sewing machines having a cup-shapedbody provided with a loop-seizing beak arranged to cast the work-limb ofa needle-thread -loop in front of the rim of the hook-body, abobbin-case journaled in said hook and restrained against rotationtherewith, said bobbin-case peripherally having a needle-thread-loopdetaining spur and a cylindrical wall adjacent to said spur andextending inwardly of the hook-body, said cylindrical wall having withinthe width thereof a sharply defined loop cast-on corner directionallyextending circumferentially of the bobbin-case and merging with theinner edge of the bobbin-case in the general direction of rotation ofthe hook.

5. A horizontal axis rotary hook for sewing machines having a cup-shapedbody provided with aloop-seizing beak arranged to cast the work-limb ofthe needle-thread-loop in front of the rim of the hook-body, abobbin-case journaled in said hook and restrained against rotationtherewith, said bobbin-case having a needle-loop detaining spur and asubstantially cylindrical wall adjacent to said spur and extending in--wardly of the hook-body, said wall having a circumferentially extendingchamfered portion adjacent its inner edge terminating in a concavesurface providing a needle-loop cast-on corner at the juncture of saidconcave surface with said cylindrical wall.

6. A horizontal axis rotary hook for sewing machines having, acup-shaped body provided with a loop-seizing beak arranged to cast thework-limb of the needle-thread-loop in front of the rim of thehook-body, a bobbin-case journaled in said hook and restrained againstrota-.

.tion therewith, said bobbin-case having a needleloop detaining spur anda substantially cylindrical wall adjacent to said spur and extendinginwardly of the hook-body, said wall having a circumferentiallyextending chamfered portion adjacent its inner edge terminating withinthe region of approximately to past the vertical, to provide aneedle-loop cast-on corner terminating in the inner edge of thebobbin-case within such region.

7. A horizontal axis cup-shapedrotary hook for sewing'machines having, aloop-seizing beak and araceway, a bobbin-case having a cylindricalbobbin-cavity coaxial with said hook and a circular bearing ribjournaled in said raceway, said rib having a gap therein to provide aloopdetaining spur, said bobbin-case having a substantially cylindricalwall supporting said bearing rib and bridging the gap in the latter, theinner edge of the cylindrical wall of said bobbincase being chamfered inthat region within the first 150 past the loop-seizing position of saidrotary hook to provide a loop cast-on corner which is inclined from apoint between the bearing rib and the inner edge of the bobbin-casetoward and meets such inner edge in the general direction of motion ofsaid rotary hook.

8. A horizontal axis cup-shaped rotary hook for sewing machines having,a loop-seizing beak and a raceway, a bobbin-case having a cylindricalbobbin-cavity coaxial with said hook and a circular bearing ribjournaled in said raceway, said rib having a gap therein to provide aloop-detaining spur, said bobbin-case having a substantially cylindricalwall supporting said bearing rib and bridging the gap in the latter, thecylindrical wall of said bobbin-case being chamfered in that region ofits inner edge within the first 150 past the loop-seizing position ofsaid rotary hook to provide a loop cast-on corner which is inclined froma point between the bearing rib and the inner edge of the bobbin-casetoward and meets such inner edge in the general direction of motion ofsaid rotary hook, the point where said corner meets said inner edgebeing disposed in that region of the bobbin-case between 100 and 150past the loop-seizing position of said rotary hook.

9. A horizontal axis cup-shaped rotary hook for sewing machines having,aloop-seizing beak and a raceway, a bobbin-case having a cylindricalbobbin-cavity coaxial with said hook and a circular bearingrib journaledin said raceway, said rib having a gap therein to provide aloop-detaining spur, said bobbin-case having a substantially cylindricalwall supporting said bearing rib and bridging the gap in the latter, thecylindrical wall surface which intersects the convex surface of thebobbin-casev to provide a sharply inclined continuation of said loopcast-on corner terminating at such inner edge.

10. A horizontal axis rotary hook for sewing machines having acup-shaped body provided with a loop-seizing beak arranged to cast thework-limb of a needle-loop in front of the rim of the hook-body, abobbin-case journaled in said hook and restrained against rotationtherewith, said bobbin-case having a needle-loop detaining spur and acircular wall peripherally of which the take-up limb of the needle-loopis initially wrapped by the hook in its loop-casting excursion, saidbobbin-case having means thereon constructed and arranged to cast saidtake-up limb off of said circular wall and onto the inner face .of thebobbin-case at a time such that the additional amount of thread pulledinto the expanding needle-loop due to the initial peripheral wrapping ofthe take-up limb thereof about the bobbincase is approximately equal tothe amount of thread additionally required by the hook subsequent tosuch time to cast the needle-loop about the bobbin-case.

11. The combination with a horizontal axis rotary hook having aloop-seizing beak and a loopcasting throat the bottom of which isangularly spaced less than 30 from the point of said beak, of astationary cylindrical thread-case having a peripheral bearing ribjournaled in said hook, said thread-case being chamfered adjacent itsinner edge to provide a sharply defined needleloop cast-on cornerbetween-said bearing rib and the inner edge of said bobbin-case, saidcast-on corner extending peripherally of the bobbin-case and having aterminal portion abruptly inclined,

toward and meeting the inner edge of said bobbincase in the generaldirection of motion of said roformed with a rotation-restraining notch,said flange having a narrow thread-guiding slot out therein alongsidesaid notch, said slot having a depth at its inner end exceeding thedepth of said notch.

CHARLES A. KESSLER.

